Honestly, that's about as balanced a system as anyone's going to get for that size. Looks good to me.
Do you not like Maths so far? If not, there are other options, of course, but that kind of patching platform is nicely consistent for this kind of classic-style modular case, especially in tandem with a different style function generator like the 281t that handles more typical, obvious stuff. This way, you can save your Maths for crazy stuff like slew limiting, creative envelope following/sidechaining, mixing, or even an extra oscillator or filter (I love the 281t but Maths is way better with audio signal stuff). They complement each other very well and cover each other's weaknesses.
Mostly I agree with you about effects, but there is one hardware effect that I think complements this system well and is worth trying: spring reverb. It just has a special glow, and you can get some great classic experimental music tones from cranking it up or playing the springs manually. It's a big part of classic Buchla sound, and they even include one in their most famous instrument, the Easel Command. It doesn't necessarily have to be in-rack (and in fact, even if you get a module for it the spring tank probably won't fit in there), but it's probably worth looking into once you feel comfy with all this. Sometimes you can find a good digital one - mostly when it emulates a specific circuit. VCV Rack has a software emulation of Befaco's Spring Thing reverb and it is surprisingly convincing. VCV Rack is also a great recommendation here for trying out kinds of modules and adding in modular effects and other DAW amenities so they can be patched togethet uniquely without buying another system - all for free, or for a decent price if you want it as a VST in your DAW rather than a standalone program.